* fix(doctor): restore the pre-migration session index when runs share a store
Restore picked the winning archive by manifest iteration order, newest first.
When a legacy writer recreated an empty sessions.json between migrations, the
newest run had archived that empty file, so restore installed it and then
refused the only archive holding real sessions as a conflict.
Resolve one winning archive per destination before writing anything, preferring
the earliest run whose archive is still restorable. Losing archives are never
deleted and stay visible as conflicts.
Closes#116163
* fix(doctor): fail closed on ambiguous session restores
* test(doctor): key restore conflicts by archive
* fix(doctor): narrow restored archive lookup
* fix(doctor): stream restore archive hashing
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Co-authored-by: Vincent Koc <vincentkoc@ieee.org>
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